The present invention relates to laser welding of gas turbine engine components and the like, and more particularly, to an improved single point powder feed nozzle for use in laser welding gas turbine engine components or other workpieces which may have a complex geometric surface contour.
There are two basic categories or types of laser welding: penetration welding and surfacing or cladding type welding.
Penetration type laser welding is typically used when joining two or more solid mating pieces of material. A laser source generates a laser beam having a selected power density which acts as a heat source at the laser focus or focal point to cause the mating surfaces of the material to melt and fuse together to produce a fusion weld. During penetration welding, the laser beam is focused onto or very near the mating surfaces of the two portions being joined. To maximize penetration of the weld into the mating surfaces and to maintain weld stability, an inert plasma suppression gas, such as helium or the like, is directed at the weld puddle or bead. The volume of the directed suppression gas may be between about 5 and about 40 cubic feet per hour (cfh). A circumferential laser spray nozzle, such as that described in U.S. Pat. No. 4,724,299, issued Feb. 9, 1988, entitled: "Laser Spray Nozzle and Method" and incorporated herein in its entirety by reference, may be used to supply the plasma suppression gas and may also be used to supply a powder filler to the weld puddle.
Surfacing or cladding type laser welding involves melting the surface of a material with a laser beam and adding a filler material to the molten material surface to produce a weld deposit of substantially the filler material on the surface of the material. A surfacing or cladding type laser welding operation may be performed after a penetration type laser welding operation to cover or clad the penetration weld to eliminate low weld conditions or to provide positive reinforcement. A circumferential powder feed nozzle may be used to supply the filler material for a surfacing or cladding type laser type operation; however, a disadvantage of circumferential nozzles is that weld spatter may be created and deposited on the surfaces of the mating component or workpiece portions adjacent to the weld bead which may require additional processing, such as grinding or the like, to provide a smooth aerodynamic surface, or to allow nondestructive testing of the weld area using x-ray, fluorescent penetrant inspection (FPI) or visual inspection methods.
A device which may substantially reduce or eliminate weld spatter and simplify nondestructive testing of the weld bead is a single point powder feed nozzle as described and claimed in U.S. Pat. No. 4,730,093 and 4,743,733, entitled: "Method and Apparatus for Repairing Metal in an Article", issued Mar. 8, 1988, assigned to the same assignee as the present invention and incorporated herein in its entirety by reference. An example of a single point powder feed nozzle 10 for use with a laser welding system 11 is shown in FIG. 1. For many surfaces, particularly straight and level surfaces, the single point powder feed nozzle 10 and/or the workpiece 12 may be oriented so that a reflected laser beam 14 reflected by the workpiece surface 16 and/or the weld puddle 18 will not strike the tip 20 of powder feed nozzle 10. When laser welding a workpiece 12 which has a complex geometric surface 16, such as a convex or concave surface as shown in FIG. 1, a reflected laser beam may be reflected by the complex workpiece surface 16 or the weld puddle 18 and may strike tip 20 of the powder feed nozzle. The heat of the reflected laser beam 14 may cause melting of the powdered filler material (not shown in FIG. 1) at the nozzle tip 20 and clogging of the nozzle orifice (not shown in FIG. 1) from which the powdered filler material is discharged.